Category

Published on

27 Aug 2015

Abstract

The 1D Heterostructure Tool is a program for the design and simulation of 1D heterostructures.

It calculates a self-consistent solution of electron density and electrostatic potential using different density models (semiclassical density, 1-band effective mass model, 10- and 20-band tight-binding models). A variety of materials lattice-matched to different substrates is available. The tool serves educational purposes as well as research questions raised by experimentalists.

A user-friendly GUI provides guidance for the straightforward handling of the tool:

Define the heterostructure by entering materials, thicknesses and doping concentrations in a table.

Choose the employed density model and temperature.

Choose more simulation options such as a ramping of the gate voltage in the case of FET cross-sections.

Gain insight into the mechanisms acting on the structure by viewing a variety of output graphs.

Starting from January 2011, the results are computed using the simulator NEMO 5.

Version History:

3.0 - Complete overhaul of the GUIs and the simulation engine. The underlying simulator is now NEMO 5. Multiband simulation capabilities using tight-binding band structure were added.

2.1.3 - New technologically relevant III-V semiconductor materials have been added. A new material substrate has been added (InAs).

2.1.2 - Graph redundancy for "Resonances/Eigenvalues vs bias " has been solved. The Graph "Eigenvalues vs bias" has been improved.

2.1.1 - The visualization of the substrate (when included) has been improved.

2.1.0 - The previous Matlab engine has been totally substituted by the C/C++ engine OMEN3D. More layers have been added. Two checkbuttons have been added for the visualization and calculation of substrate respectively. The layer L01 is now longer in the first default example. Two new graphs have been added, the first one shows the eigenenergies in function of the bias, the second one shows the resonances in function of bias. The resonance finder algorithm has been greatly improved. It is possible now to specify the range of energy where the resonances have to be searched.

2.0.4 - Valence band graph has been added. The Tk GUI code makes a difference between alloys and non-alloy materials. No need to specify a "X-mole fraction" value when a material is not an alloy. Graphs are now reflected to be consistent with the direction of x-axis in the Rappture GUI. Hamiltionian constructor has been modified according to Frensley's formulation.

2.0.3 - The materials are inserted in the grid with the following prioprity 1 - Clicked Material entry 2 - Selected layer 3 - First non-empty row The Doping Density graph is in logarithmic scale.

2.0.2 - The Material table is now more intuitive. If no layer is selected, the next layer to be filled, when the user clicks on the table, is the first non-empty one. If a layer is selected and the user clicks on the material list then the selected layer is to be filled.

2.0.1 - The density graph has been improved.

2.0 - Complete overhaul of the structure entry. A friendly Tcl/Tk GUI implemented in which materials can be added to a simple, table-based list from a material list defined in a database. The list is currently limited to materials grown unstrained on a GaAs substrate. The computational kernel is modified to take into account many different materials. There are 2 different HFET designs, as QWIP design and QCL design provided as an input.

1.0.3 - Fermi-Dirac distribution implemented.

1.0.2 - Plotting of data has been improved and should now be much faster.

1.0.1 - The charge calculation for the low temperature case has been corrected.

Outlook:
Several improvements are planned for the future:

Ternary materials

Holes

Strain

Varying crystal orientations

Non-zincblende crystals

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NEMO 5, a code under development in the research group of Gerhard Klimeck. NEMO 5 is an open source nanoelectronics device simulator containing a variety of different material and geometry models. Features include the construction of atomistic grids of varying crystal structures, multiband Schroedinger-Poisson simulations, atomistic strain and phonon computations, quantum transport using open-boundary wavefunctions or NEGF, and user-friendly input/output.